Exemplary embodiments relate to a semiconductor memory device and a method of operating the same.
Semiconductor memory devices are storage devices in which data can be stored and from which the data can be read. Examples of the semiconductor memory devices are Random Access Memory (RAM) and Read Only Memory (ROM). As to RAMs, data stored therein are erased when the supply of power is stopped. This type of memory is referred to as volatile memory. As to ROMs, data stored therein is not erased when the supply of power is stopped. This type of memory is referred to as a nonvolatile memory.
As to semiconductor memory devices, functions that the semiconductor memory device performs increase proportionally to an increase in the integration, capacity, and chip size.
In order to further increase the degree of integration of semiconductor memory devices, a multi-bit cell capable of storing plural bits of data in one memory cell are used as opposed to a memory cell capable of storing a single bit (“a single level cell”).
The multi-level cell has a plurality of threshold voltages corresponding to the number of bits storable in the multi-level cell. In achieving higher integration, the threshold gaps between the threshold voltages become increasingly narrow.
Here, prevention of the threshold voltages of memory cells from being changed due to the capacitive coupling resulting from the threshold voltages of neighboring memory cells during a program operation in a semiconductor memory device is useful.